What you carry at this position in your DNA and what research says about it.
Autoimmune and Asthma Risk: 5/10 evidence, 29 publications.
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Sample genotype (not yours): T/T
Typical Immune and Drug Response
Typical baseline risk for immune-mediated conditions is expected with this genotype. A typical response to morphine is expected, with a standard risk of common side effects.
What this genotype means: Typical risk of type-1 diabetes; Typical risk of allergic asthma; Typical morphine response.
Sample genotype (not yours): C/C
Lowest Autoimmune Risk and Optimal Morphine Tolerability
Carrying two copies of the protective C allele is associated with the lowest risk of type-1 diabetes and allergic asthma. It also correlates with the best tolerability and lowest side-effect rate for morphine.
What this genotype means: Lowest risk of type-1 diabetes; Lowest risk of allergic asthma; Minimal morphine-related side effects.
Sample genotype (not yours): T/C
Lower Autoimmune Risk and Better Morphine Tolerability
Carrying one copy of the protective C allele is linked to a lower risk of type-1 diabetes and allergic asthma. It is also associated with a reduced likelihood of side effects when taking morphine.
What this genotype means: Reduced risk of type-1 diabetes; Reduced risk of allergic asthma; Fewer morphine-related side effects.
Gene function and biological role
Gene Function: The TLR2 gene encodes Toll-like receptor 2, a critical protein of the innate immune system. This receptor sits on the surface of immune cells where it detects foreign pathogens like bacteria and fungi [1]. Once activated, it triggers inflammatory pathways to help the body fight off infections [2]. However, variations in how this receptor functions can influence susceptibility to autoimmune conditions and inflammatory disorders [1]. It also plays a role in neuroimmune pathways that interact with certain medications [3].
Variant Impact: The rs3804100 variant is a synonymous change in the TLR2 gene, meaning it does not alter the amino acid sequence of the receptor protein. Despite not changing the protein structure, this genetic variation can influence gene expression levels or translation efficiency [1]. The major T allele is widely common, whereas the minor C allele is less frequent globally [4]. Research indicates that carrying the C allele is associated with a protective effect against certain immune-mediated conditions [1]. Additionally, this variant has been linked to differences in how the body tolerates pain medications like morphine [3].
Key Insight: Carrying the minor C allele of this immune receptor variant simultaneously lowers the risk of developing type-1 diabetes and allergic asthma, while also reducing the likelihood of side effects from morphine.
Location: TLR2. Chromosome 4 · 4q31.3 · 153.7 Mb
Estimated prevalence by population
Global 86.5%; European 86.7%; African 89.7%; East Asian 55.6%; South Asian 72.5%; Americas 86.4%; Ashkenazi 87.5%; Finnish 93.5%; Middle Eastern 77.0%; Amish 97.8%.
Estimated TT genotype frequency.
Global 12.9%; European 12.9%; African 10.1%; East Asian 37.9%; South Asian 25.3%; Americas 13.1%; Ashkenazi 12.1%; Finnish 6.4%; Middle Eastern 21.5%; Amish 2.2%.
Estimated TC genotype frequency.
Global 0.7%; European 0.5%; African 0.3%; East Asian 6.5%; South Asian 2.2%; Americas 0.5%; Ashkenazi 0.4%; Finnish 0.1%; Middle Eastern 1.5%; Amish < 0.1%.
Estimated CC genotype frequency.
Showing effects for T/T genotype
Cardiovascular & Metabolic
Diabetes & Glycemic Traits
Type 1 Diabetes. Evidence: 3/10. Source: PMID 19148143. Typical Risk.
Organ Systems
Respiratory Health
Asthma. Evidence: 3/10. Source: PMID 19148143. Typical Risk.
Pharmacogenomics
Pain Medication Response
Morphine Side Effects. Evidence: 5/10. Source: PMID 27649267. Typical.
Lifestyle, Fitness & Aging
Height & Body Size
Height. Evidence: 4/10. Source: PMID 36224396. Typical.
Showing effects for C/C genotype
Type 1 Diabetes. Evidence: 3/10. Source: PMID 19148143. Lowest Risk.
Asthma. Evidence: 3/10. Source: PMID 19148143. Lowest Risk.
Morphine Side Effects. Evidence: 5/10. Source: PMID 27649267. Better Tolerability.
Height. Evidence: 4/10. Source: PMID 36224396. Taller.
Showing effects for T/C genotype
Type 1 Diabetes. Evidence: 3/10. Source: PMID 19148143. Lower Risk.
Asthma. Evidence: 3/10. Source: PMID 19148143. Lower Risk.
Height. Evidence: 4/10. Source: PMID 36224396. Slightly Taller.
What this genotype means for the people who carry it
Sample genotype: TT (Homozygous)
Carrying two copies of the common T allele represents the baseline genetic profile for the majority of the population. Studies show that this genotype is associated with a typical baseline risk for developing type-1 diabetes and allergic asthma [1]. In terms of pain management, individuals with this profile generally show a typical response to morphine [2]. They also experience a typical likelihood of experiencing common morphine-related side effects, such as nausea, fatigue, and constipation [3]. This genetic profile is highly common across all global ancestries [4].
Typical risk of type-1 diabetes; Typical risk of allergic asthma; Typical morphine response.
Sample genotype: CC (Homozygous)
Carrying two copies of the protective C allele offers the strongest genetic defense against specific immune-mediated disorders. Clinical studies have demonstrated that this genotype correlates with the lowest risk of developing type-1 diabetes and allergic asthma [1]. When undergoing pain management with morphine, individuals with this profile typically achieve pain control with lower doses [2]. They also enjoy a significantly reduced rate of adverse effects, such as nausea, fatigue, and cognitive impairment [3]. This genotype is relatively rare, occurring in less than one percent of most populations, though it is slightly more common in individuals of East Asian descent [4].
Lowest risk of type-1 diabetes; Lowest risk of allergic asthma; Minimal morphine-related side effects.
Sample genotype: TC (Heterozygous)
Having one copy of the minor C allele provides a protective buffer against several inflammatory and autoimmune conditions. Research indicates that this genotype is associated with a significantly reduced risk of developing type-1 diabetes and childhood allergic asthma compared to the typical genotype [1]. In clinical settings, individuals with this profile are often more sensitive to morphine for pain relief [2]. They also exhibit a decreased likelihood of experiencing common morphine-induced side effects, including nausea, cognitive clouding, and constipation [3]. This genetic variation is present in about seven percent of the global population, with higher frequencies in East Asian and South Asian ancestries [4].
Reduced risk of type-1 diabetes; Reduced risk of allergic asthma; Fewer morphine-related side effects.
Variants with shared genetic architecture
rs11938228 · TLR2 Gene · Chr 4 · Anti-TNF Therapy Response
rs1898830 · TLR2 Gene · Chr 4 · Genital Herpes Severity
rs3804099 · TLR2 Gene · Chr 4 · Colon Cancer Risk
A TLR2 polymorphism is associated with type 1 diabetes and allergic asthma.
Genetic variation and haplotype structures of innate immunity genes in eastern India.
Content updated August 2026.
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